Centerless circular grinder

ABSTRACT

IMPROVED CENTERLESS CIRCULAR GRINDER ASSEMBLY, CONTROL MECHANISM, DRIVE, AND METHOD OF OPERATION FOR HIGH OUTPUT GRINDING IN WHICH THE BASIC UNITS (GRINDING WHEEL, REGULATING WHEEL AND WORKHOLDER) ARE CONTROLLABLY MOVABLE WITH RELATION TO EACH OTHER DURING GRINDING TO PERMIT HIGH RADIAL REMOVAL OF MATERIAL TO SMALLER FINISHED WORKPIECE DIAMETER.

Nov. 9, 1971 E. ROTZOLL 3,618,266

CENTERLESS CIRCULAR GRINDER Filed March 14, 1969 2 Sheets-Sheet 1 I 1 INVENTOR.

Nov. 9, 1971 E. ROTZOLL 3,618,256

CENTERLESS CIRCULAR GRINDER Filed March 14, 1969 2 Sheets-Sheet 2 IN VEN TOR.

Er/d fial'zalt Flam {m'am United States Patent 3,618,266 CENTERLESS CIRCULAR GRINDER Erich Rotzoll, Hannover-Kirchrode, Germany, assignor to Herminghausen-Werke GmbH, Hannover, Germany Filed Mar. 14, 1969, Ser. No. 807,361 Claims priority, application Germany, Mar. 14, 1968, P 16 52 066.4 Int. Cl. B24b /18 US. Cl. 51-103 R 5 Claims ABSTRACT OF THE DISCLOSURE Improved centerless circular grinder assembly, control mechanism, drive, and method of operation for high output grinding in which the basic units (grinding wheel, regulating wheel and workholder) are controllably movable with relation to each other during grinding to permit high radial removals of material to smaller finished work piece diameter.

The invention relates to centerless circular grinders, in which the grinding wheel and the regulating wheel are horizontally spaced apart with the workpiece holder arranged therebetween. More particularly, the invention is concerned with providing improved centerless circular grinder assemblies, control mechanisms, drives and methods" of operation for high output grinding in which the wheels and workholder are controllably movable during grinding for high amounts of radial removal of materials.

Grinders of this general type in which the workpiece center is not fixed are well known in a number of differing designs. In one type there is provided a workpiece support arranged stationary with reference to the machine bed, while the grinding wheel and the regulating wheel are each borne on a slidable headstock movable relative to the workpiece support by means of a slide on the bed. In a second type the grinding wheel is borne in a stationary headstock, and the workpiece support is slidably carried on the bed relative to the grinding wheel headstock by means of a first slide. In this system a headstock for the regulating wheel is slidably borne by means of a second slide on the workpiece supporting slide. Finally, a third type, like the second, again has a stationary grinding wheel headstock, and differs from the second substantially only in that the slide of the regulating wheel headstock is carried on the bed and the workpiece support slide is in turn carried on the slide of the regulating wheel headstock.

The manner of operation of all of these conventional grinders is the same in principle, even though in each case there is provided a different machine actuation corresponding to each type. In the type having a stationary workpiece support the regulating wheel is first shifted on the bed against the workpiece placed on the workpiece support in such a way that it brings the workpiece into a position in which the working line or face of the workpiece, -i.e., the workpiece surface line interacting with the grinding wheel, projects sufiiciently beyond that edge of the workpiece support which faces the grinding wheel. According to this system, the grinding wheel and regulating wheel are driven at a speed differing from one another. The grinding wheel is brought up to the workpiece, with the regulating wheel remaining stationary, until the workpiece is ground to the desired dimension. In the second and third types of grinder, those having a stationary grinding wheel headstock, the adjustment to the workpiece diameter for the initial set-up takes place in an analogous manner with the regulating wheel and workpiece support being shifted relative to one another. Then these two parts are joined together by a clamping of their slides to form a ice common block, which as such is brought up to the grinding wheel. In all three cases, accordingly, there is provided relative movement between regulating wheel and workpiece support only before grinding for the purpose of the adjustment of the workpiece diameter. Further, during the grinding, the position of the regulating wheel with respect to the workpiece support is maintained unaltered and the feed lmovement consists only in a relative movement of grinding wheel and workpiece support.

Now, the constant position of the regulating wheel with respect to the workpiece support causes a shifting of the workpiece from its initial position toward the regulating wheel as a consequence of the diminishing workpiece diameter during grinding. So long as the grinding job requires only relatively small radial removal of material, of which hitherto the centerless grinders were only capable, this phenomenon is not troublesome, because the displacement of the workpiece axis in the grinding process is so slight that it can be directly compensated for by a corresponding feed movement. This phenomenon, however, makes grinding with high radial material removals virtually impossible since as a consequence of the great alterations in diameter of the workpiece, the displacement of the workpiece axis becomes so great that it can no longer be compensated for by the feed movement. The surface of the workpiece in contact with the grinding wheel will recede past the edge of the workpiece support facing the grinding wheel before the grinding operation has been completed. It may be thought that this drawback could be remedied by arranging the workpiece in such a way that from the outlet the workpiece surface, in contact with the grinding wheel, will project sufficiently far beyond the edge of the workpiece support facing the grinding wheel. However, this is not possible, inter alia, because of the interference between the workpiece support and the regulating wheel which would arise during grinding.

Recently there has been introduced so-called highoutput grinding which operates with very high speed grinding wheels. By means of such high-output grinding it is in principle economically feasible to use a grinding process for high radial amounts of material removal (instead, say, of turning processes or the like used hitherto).

Accordingly, it is among the objects of this invention to make the conventional types of grinders defined above, which have long proved successful, suitable for high radial material removal without special additional expenditure.

Another object is to provide an apparatus for high radial material removal grinding.

It is another object to provide an improved control means for conventional centerless grinders of low radial material removal capacity which adapts them for high output grinding.

Still further objects will be apparent from the detailed description which follows.

These objects are achieved according to this invention by providing means for driving the workpiece support and the regulating wheel slidably relative to one another during the grinding so that the surface line of the workpiece in contact with the grinding wheel may be continuously maintained beyond that edge of the workpiece support which faces the grinding wheel.

Further details and advantages of the invention are explained in the following detailed description with reference to drawings illustrative of several embodiments in which:

FIG. 1 schematically represents a first embodiment of a centerless circular grinder according to this invention;

FIG. 2 schematically represents a second embodiment of a centerless circular grinder according to the invention;

FIG. 3 schematically represents a third embodiment of a centerless circular grinder according to the invention;

FIGS. 4a, 4b, and 5 show in detail representations for the explanation of the manner of functioning of the invention.

The principles of this invention are consistently contrary to the principles of the prior conventional devices and methods wherein the position of the regulating wheel is left constant with respect to the workpiece support during the grinding. Instead of that, this invention provides a relative drive between regulating wheel and workpiece support, by which the distance between regulating wheel and workpiece support is reduced and controlled during the grinding operation. This results in a movement of the workpiece, on the workpiece support, which is in a direction opposite to the retreat of the workpiece, resulting from the reduction in diameter during grinding. This movement can be adjusted and controlled without difficulty in such a way so that the workpiece surface line in contact with the grinding wheel always projects sufficiently for beyond the edge of the workpiece support facing the grinding wheel. This control is possible in every case, even with high radial removals of material in high-output grinding.

In its practical execution this invention requires only a minimal expenditure which, in view of the fact that a new area of utilization is opened up to the machine, is of no consequence whatever. Since a relative slidability of regulating wheel and workpiece support is present anyway in conventional grinders, there needs to be provided between these two parts only a shifting drive which is operable during the grinding. This drive mechanism can be constructed in a manner usual for the drive of the feed movement, or it can be derived directly from the feed drive. 'Other fundamental modifications of the machine construction are not required, so that by means of this invention there is yielded the further advantage that, if need be, even prior conventional grinders using a high-speed grinding wheel to obtain improved grinding quality rather than for high radial removals of material can be converted in a simple manner for high radial removals of material. However, added control means for the drives may be provided.

Referring now to the drawings, the grinders represented in FIGS. 1 to 3 have numerous features in common. In each case there is provided a machine bed 1 which carries a grinding wheel headstock 2 and a regulating wheel headstock 3, as well as a workpiece support 4 disposed in the middle between the two headstocks. A grinding wheel 6 is rotatably borne in the grinding wheel headstock 2. In such systems the drive devices, necessary or posible aligning devices, and other parts related to the grinding wheel operation are likewise arranged in this headstock. In a corresponding manner a regulating wheel 7 is borne in the regulating wheel headstock 3. The workpiece support 4 has on its upper end a supporting surface 5 sloping obliquely downward toward the regulating wheel 7. This surface serves for the support and guidance of the workpiece 8 during the grinding process.

In the form of construction according to FIG. 1, the grinding wheel headstock 2 and the regulating wheel headstock 3 are secured in each case to slides, which are slidable by means of suitable guides 11 and 12, respectively, along the machine bed 1 toward or away from the stationary workpiece support 4. In the embodiment or form shown according to FIG. 2, the grinding wheel headstock 2 is connected to the machine bed 1 to be stationary or fixed. Both the workpiece support 4 and the regulating Wheel headstock 3 are slidably arranged on the machine bed through means of a slide guide 13, and a separate slide guide 14 on the workpiece support slide, respectively. The embodiment according to FIG. 3 corresponds for the most part to the embodiment of FIG. 2, with the difference that the regulating wheel headstock 3 is Supported on a slide guide 15 slidably mounted on the machine bed 1, and the workpiece support 4 in turn is supported on a slide guide 16 slidably mounted on the slide of the regulating wheel headstock 3.

All the above-mentioned slide guides 11 to 16 may take any suitable form; they can, for example, be slide guides, roller guides, or hydrostatic guides, and are, therefore, only schematically indicated. correspondingly, the other parts 1 to 8 of the machine, which are likewise only schematically represented, can have any suitable construction such as are already known in numerous variants.

It was already mentioned that the basic parts of the embodiment of the grinder shown in FIG. 1 heretofore was operated in such a way that first, by sliding of the regulating wheel headstock 3 in relation to the workpiece support 4, the machine was set tip for the desired workpiece diameter. Then the regulating wheel headstock 3 was clamped securely in a fixed position on the machine bed 1. Thereafter the grinding wheel 6 was brought up to the workpiece 8 by sliding of the grinding wheel headstock 2 through actuation of a feed gear 20 (which, again, can have any suitable type of construction and, for this reason, is only schematically represented). As a consequence of the distance between the regulating wheel 7 and the workpiece support 4 remaining constant in the manner of operation, only limited material removal performances are possible, as FIG. 4a illustrates in a somewhat exaggerated representation. In FIG.4a the contours of the grinding wheel and of the workpiece before commencing the actual grinding operation are represented in dot-and-dashed lines. The contours of the parts after completion of grinding are represented in solid lines. It can be seen that the feed movement of the grinding wheel must be limited when the workpiece 8, as a consequence of its diminishing diameter, has fallen back so far on the slope 5 of the workpiece support that its surface line 9 interacting or in contact with the grinding wheel lies approximately in the region of'the edge 42. of the workpiece support which faces the grinding wheel. As soon as this position is reached, no further grinding can take place since then the grinding wheel 6 would collide with the edge 4a of the workpiece support.

In view of this, in the embodiment of FIG. 1, the invention is realized by providing the regulating wheel headstock 3 with a shifting, or lateral movement, gear or drive mechanism. This may be, for example, a second gear 21 like the feed gear 20. Alternatively, this drive can be derived directly from the feed drive 20 via an adjustable or extensible driver 22, and via intermediate gearing, if needed. The initial setting up of the machine to the workpiece diameter is done in the same manner as heretofore, i.e., by lateral shifting or movement of the regulating wheel headstock 3. For the grinding process, however, the regulating wheel headstock is now no longer clamped securely to the machine bed 1 in stationary position, but it undergoes, by means of the driving or lateral shifting gear 21 or 22, a controlled and/or continuous advance, which is directed opposite to the falling back of the workpiece 8 on the slope 5. This provides that the contact surface line 9 of the workpiece remains continuously beyond the edge 4a of the workpiece support 4 during the entire duration of the grinting process. Thus, during the grinding, not only is the grinding wheel 6 brought up, i.e., advanced laterally, but also a shifting or movement of the regulating wheel relative to the workpiece support occurs.

The effect of the relative movement between regulating wheel 7 and workpiece support 4 can be seen easily in FIG. 4b. There again the initial positions of the parts are represented in dot-and-dashed lines and the final positions are represented in solid lines. A comparison of FIGS. 4a and 4b makes clear immediately that with the same amount of feed movement of the grinding wheel 6, very much higher material removal performances are achievable on the workpiece 8 with this invention, and the workpiece, therefore, can be ground down to a very much smaller diameter.

The preceding description is likewise true also for the embodiments of FIGS. 2 and 3. For these embodiments the procedure heretofore followed for the setting up of the machine for the workpiece diameter involved, first, the shifting or movement of the regulating headstock 3 relative to the workpiece support 4. Then the regulating wheel headstock and workpiece support were clamped together to form a solid or unitary block, and this block, finally, was brought up to the stationary grinding wheel 6 by means of a feed drive gear 23. For both these forms of construction, according to this invention, I now provide that after the setting up of the machine, the clamping of regulating wheel headstock and workpiece support is eliminated. Instead of this, during the grinding these two parts are shifted or moved relative to one another in order to compensate for the dropping back of the workpiece on the workpiece support as a result of material removal. The shifting gear drive for the relative shifting between regulating wheel headstock 3 and workpiece support 4 may be derived directly, if need be, over an intermediate gear, from the feed drive 23 as shown in FIGS. 2 and 3. It is also possible to provide each of these two parts with a separate drive (not shown in the figures).

The machines of FIGS. 2 and 3 according to the invention have, in principle, the effect already explained with the aid of FIG. 4b, with the sole distinction that the grinding wheel 6 remains stationary. The .feed movement consists of a corresponding displacement of the workpiece support and of the regulating wheel toward the grinding wheel. In addition, the regulating wheel while being brought up, executes a compensating relative movement toward the workpiece support 4.

In addition, the invention makes possible still another manner of operation of the machines of the embodiments shown in FIGS. 2 and 3. This method is advantageous in the individual cases, and is explained in FIG. 5. In the method of operation according to FIG. 5, the relative movement between workpiece support 4 and regulating wheel 7 is not produced by continuously bringing up the regulating wheel to the workpiece support during the grinding with the workpiece support in the process carrying out the normal feed movement, but rather by the feature that during the grinding the workpiece support is moved away from the grinding wheel toward the regulating wheel and the regulating wheel on its part executes the normal feed movement. The result of the manner of operation according to FIG. 5 is of course like the manner of operation according to FIG. 411.

Furthermore, in the embodiment according to FIG. 1 the invention makes possible an alternative method of operation. By the invention one may proceed in such a way that for the setting up of the machine to the workpiece diameter, first, the grinding wheel 6 is shifted toward the workpiece support 4 and it is then clamped fast to the adjusted position on the machine bed. Then the regulating wheel headstock 3 is shifted or brought up, in which step the regulating wheel headstock executes a somewhat increased advance movement, as compared to the normal bringing-up movement, which compensates for the falling-back of the workpiece on the workpiece support. This alternative manner of operation is in certain cases advantageous for certain types of work, and is immediately understood if, in FIG. 5, the workpiece support is thought of as stationary. Accordingly, this alternative manner of operation is also possible in the machines of FIGS. 2 and 3, by maintaining the workpiece support in a constant spacing with respect to the grinding wheel 6 during the grinding.

The extent of the relative additional movement required in the process of this invention between regulating wheel and workpiece support as compared to the extent of the normal feed movement depends essentially on the angle of inclination of the support slope or bevel 5, on the diameter of the workpiece 8, and on the position of the workpiece axis with respect to the common axial plane of regulating wheel and grinding wheel. In each individual case the relative movement actually required between regulating wheel and workpiece support according to these parameters can be determined fairly simply. The drive means 20, 21 and 23 may be provided with control means for continuous or predetermined feed rates during the grinding, e.g. as by constant or variable rate feed screws powered from a single or separate sources.

I claim:

1. In a centerless circular grinder including:

(a) a machine bed,

(b) a grinding wheel headpiece having a grinding wheel rotatably mounted thereon, said grinding wheel headpiece being disposed in operative relation to said bed,

(0) a regulating wheel headpiece having a regulating wheel rotatably mounted thereon, and means for laterally moving said regulating wheel headpiece with respect to said bed, said regulating wheel headpiece being disposed in operative relation to said bed, and

(d) a workpiece holder for supporting a workpiece having an edge facing said grinding wheel, and means for laterally moving said workpiece with respect to said bed, the improvement which comprises in combination:

(e) means for driving and positively controlling, at a predetermined rate at least two of:

(i) said grinding wheel headpiece,

(ii) said regulating wheel headpiece, and

(iii) said workpiece holder relative to each other,

during grinding to (1) provide relative movement between both said grinding wheel and said workpiece holder, and between said regulating wheel and said workpiece holder, and to:

(2) maintain a grinding surface line, defined by contact of a workpiece and said grinding wheel, between said edge of said workpiece holder and said grinding wheel,

thereby permitting high radial material removal and reduction of the diameter of said workpiece to substantially the width of said workpiece holder.

2. A grinder as in claim 1 wherein said grinding wheel headpiece includes means for lateral movement thereof relative to said bed, and said drive means actuates said grinding wheel headpiece during grinding operations.

3. A grinder as in claim 2 wherein said drive means also drives said regulating wheel headpiece during grinding operations.

4. A grinder as in claim 1 wherein said grinding wheel head is fixed relative to said bed, and said drive means actuates said workpiece holder and said regulating wheel headpiece to provide relative lateral movement thereof during grinding.

5. A grinder as in claim 4 wherein said workpiece holder is slidably mounted on said regulating wheel headpiece.

References Cited UNITED STATES PATENTS 1,264,930 5/1918 Heim 5 1--103 1,585,984 5/1926 Heim 51-103 X 1,777,607 10/ 1930 Ekholm et a1 51-103 1,924,593 8/ 1933 Binns 51-103 2,861,399 11/ 1958 Lundius 51-403 LESTER M. SWINGLE, Primary Examiner 

